1. Field of the Invention
The present invention relates generally to pre-engineered roof systems, and more particularly but not by way of limitation, to an improved standing seam roof assembly and components thereof.
2. Discussion of the Prior Art
In erecting a roof of a pre-engineered structure the established method is to erect the primary structural members, attach the secondary structural members to the primary structural members, and secure appropriate bracing members. Blanket-type or rigid insulation is then positioned across the secondary structural members and the roof panel members are positioned over the insulation. Thereafter, the roof panel members are connected to each adjacently disposed roof panel member and to the secondary structural members.
The prior art is replete with various types of roof assemblies which have heretofore been proposed for a pre-engineered roof system in an effort to provide a water-tight roof assembly, while at the same time enabling the roof assembly to expand and contract due to changes of temperature or forces applied to the roof assembly. Typical of such a prior art roof assembly which has been widely accepted in recent years is the standing seam roof assembly.
In a standing seam roof assembly the panel members are joined to each other along adjacent sides so that the sides are locked together to form the standing seams. The panel members are secured to the secondary structural members by clips that extend into the standing seam. The interconnection of the panel members and clips lends stiffness and strength to the roof structure, and permits the roof structure to expand and contract as a function of the coefficient expansion of the materials from which the roof panels are fabricated, as well as the temperature cycles to which the roof panels are exposed, independent of expansion and contraction of the secondary and primary structural members. The standing seam roof assembly is also subjected to other forces, such as wind uplift forces and load forces created by rain, snow or a workman walking on the roof panels.
Repeated occurrence of uplift and load forces on the panel members tends to weaken the panel-to-panel lap joint and causes the panels to separate which results in structural failure and leaks. Leaks in the roof assembly are usually caused by separation of the panel-to-panel lap joint from contact with the sealant used at the joints.
In an effort to overcome the deterioration of the panel-to-panel lap joint of the prior art roof assemblies, attempts have been made to modify the sealant employed to seal such joints in order to improve adhesion, flexibility and water repellency of the sealant. Further, the design of such joints has been such that the pressure on the sealant varied greatly at the clip locations throughout the length of the side lap joints of the panel which resulted in uneven distribution of pressure on the sealant and voids in the joints, either of which frequently led to leaks.
While advancement has been made in the design of roof assemblies for pre-engineered structures, and particularly in the design of the panel-to-panel lap joint, the need remains for an improved standing seam roof assembly which has a positive locking action with improved resistance to unsnapping, while reducing the critical tolerance requirements for sealant of the prior art panel-to-panel lap joints of the standing seam roof assemblies, and which provides a continually compressed gasket seal for the joint when the panels of the roof assembly are at rest, or when the panels are subjected to live loads, to uplift forces or to roof traffic. It is to such an improved standing seam roof assembly that the present invention is directed.